/*
 * Copyright (C) 2013 Adrian Ulrich <adrian@blinkenlights.ch>
 *
 * This program is free software: you can redistribute it and/or modify
 * it under the terms of the GNU General Public License as published by
 * the Free Software Foundation, either version 3 of the License, or
 * (at your option) any later version.
 *
 * This program is distributed in the hope that it will be useful,
 * but WITHOUT ANY WARRANTY; without even the implied warranty of
 * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
 * GNU General Public License for more details.
 *
 * You should have received a copy of the GNU General Public License
 * along with this program. If not, see <http://www.gnu.org/licenses/>.
 */

package net.nullsum.audinaut.util.tags;

import java.io.IOException;
import java.io.RandomAccessFile;
import java.nio.charset.StandardCharsets;
import java.util.ArrayList;
import java.util.HashMap;
import java.util.Locale;


class ID3v2File extends Common {

    public ID3v2File() {
    }

    public HashMap getTags(RandomAccessFile s) throws IOException {
        HashMap tags;

        final int v2hdr_len = 10;
        byte[] v2hdr = new byte[v2hdr_len];

        // read the whole 10 byte header into memory
        s.seek(0);
        s.read(v2hdr);

        int v3len = ((b2be32(v2hdr, 6)));          // total size EXCLUDING the this 10 byte header
        v3len = ((v3len & 0x7f000000) >> 3) | // for some funky reason, this is encoded as 7*4 bits
                ((v3len & 0x007f0000) >> 2) |
                ((v3len & 0x00007f00) >> 1) |
                ((v3len & 0x0000007f));

        // debug(">> tag version ID3v2."+id3v);
        // debug(">> LEN= "+v3len+" // "+v3len);

        // we should already be at the first frame
        // so we can start the parsing right now
        tags = parse_v3_frames(s, v3len);
        tags.put("_hdrlen", v3len + v2hdr_len);
        return tags;
    }

    /* Parses all ID3v2 frames at the current position up until payload_len
     ** bytes were read
     */
    private HashMap parse_v3_frames(RandomAccessFile s, long payload_len) throws IOException {
        HashMap tags = new HashMap();
        byte[] frame = new byte[10]; // a frame header is always 10 bytes
        long bread = 0;            // total amount of read bytes

        while (bread < payload_len) {
            bread += s.read(frame);
            String framename = new String(frame, 0, 4);
            int slen = b2be32(frame, 4);

            /* Abort on silly sizes */
            if (slen < 1 || slen > 524288)
                break;

            byte[] xpl = new byte[slen];
            bread += s.read(xpl);

            if (framename.substring(0, 1).equals("T")) {
                String[] nmzInfo = normalizeTaginfo(framename, xpl);

                for (int i = 0; i < nmzInfo.length; i += 2) {
                    String oggKey = nmzInfo[i];
                    String decPld = nmzInfo[i + 1];

                    if (oggKey.length() > 0 && !tags.containsKey(oggKey)) {
                        addTagEntry(tags, oggKey, decPld);
                    }
                }
            }
        }
        return tags;
    }

    /* Converts ID3v2 sillyframes to OggNames */
    private String[] normalizeTaginfo(String k, byte[] v) {
        String[] rv = new String[]{"", ""};
        HashMap lu = new HashMap<String, String>();
        lu.put("TIT2", "TITLE");
        lu.put("TALB", "ALBUM");
        lu.put("TPE1", "ARTIST");

        if (lu.containsKey(k)) {
            /* A normal, known key: translate into Ogg-Frame name */
            rv[0] = (String) lu.get(k);
            rv[1] = getDecodedString(v);
        } else if (k.equals("TXXX")) {
            /* A freestyle field, ieks! */
            String[] txData = getDecodedString(v).split(Character.toString('\0'), 2);
            /* Check if we got replaygain info in key\0value style */
            if (txData.length == 2) {
                if (txData[0].matches("^(?i)REPLAYGAIN_(ALBUM|TRACK)_GAIN$")) {
                    rv[0] = txData[0].toUpperCase(); /* some tagwriters use lowercase for this */
                    rv[1] = txData[1];
                } else {
                    // Check for replaygain tags just thrown randomly in field
                    int nextStartIndex;
                    int startName = txData[1].toLowerCase(Locale.US).indexOf("replaygain_");
                    ArrayList<String> parts = new ArrayList<>();
                    while (startName != -1) {
                        int endName = txData[1].indexOf((char) 0, startName);
                        if (endName != -1) {
                            parts.add(txData[1].substring(startName, endName).toUpperCase());
                            int endValue = txData[1].indexOf((char) 0, endName + 1);
                            if (endValue != -1) {
                                parts.add(txData[1].substring(endName + 1, endValue));
                                nextStartIndex = endValue + 1;
                            } else {
                                break;
                            }
                        } else {
                            break;
                        }

                        startName = txData[1].toLowerCase(Locale.US).indexOf("replaygain_", nextStartIndex);
                    }

                    if (parts.size() > 0) {
                        rv = new String[parts.size()];
                        rv = parts.toArray(rv);
                    }
                }
            }
        }

        return rv;
    }

    /* Converts a raw byte-stream text into a java String */
    private String getDecodedString(byte[] raw) {
        int encid = raw[0] & 0xFF;
        int len = raw.length;
        String v = "";
        try {
            int ID3_ENC_LATIN = 0x00;
            int ID3_ENC_UTF8 = 0x03;
            int ID3_ENC_UTF16BE = 0x02;
            int ID3_ENC_UTF16LE = 0x01;
            if (encid == ID3_ENC_LATIN) {
                v = new String(raw, 1, len - 1, StandardCharsets.ISO_8859_1);
            } else if (encid == ID3_ENC_UTF8) {
                v = new String(raw, 1, len - 1, StandardCharsets.UTF_8);
            } else if (encid == ID3_ENC_UTF16LE) {
                v = new String(raw, 3, len - 3, StandardCharsets.UTF_16LE);
            } else if (encid == ID3_ENC_UTF16BE) {
                v = new String(raw, 3, len - 3, StandardCharsets.UTF_16BE);
            }
        } catch (Exception ignored) {
        }
        return v;
    }

}
